It is already known in the art of vehicles such as automobiles to calculate a target steering angle of steered wheels of the vehicle by an electronic control device based upon the running state of the vehicle and to steer the steered wheels by a steer driving device so that the steering angle of the steered wheels becomes the target steering angle.
On the other hand, as one of the steering control devices for vehicles, it is proposed in Japanese Patent Laid-open Publication Hei 11-157461 filed by the same applicant as the present application to provide a mechanism for variably changing the transmission ratio in the steering of the steered wheels by the force of a driving source in a manner of decreasing the transmission ratio when the steering angle of the steered wheels approaches the maximum steering angle for the purpose of protecting the steer driving device. By such a steering control device it is avoided that an excessive load is imposed on the steering mechanism by the steer driving device being actuated when the steered wheels are steered to the maximum steering angle.